Internet Protocol (IP) telephone systems such as Skype (registered trademark) have become commonplace in recent years. The IP telephone system can be used simply by installing an IP telephone application on a PC or other network terminal, where the IP telephone application is software developed by the IP telephone provider for originating and receiving calls and implementing voice communications.
Japanese patent application publication No. 2005-192086 describes one such IP telephone system having a server that registers information on network terminals. With this system, each transceiver terminal is provided with a function for referencing the information registered on the server. Therefore, the user can acquire information on other terminals and can transmit data that the other terminals can process. Japanese patent application publication No. 2005-080025 discloses other related technologies for IP telephones.
However, it is difficult to learn information about other callers in the conventional IP telephone systems. Specifically, one caller either cannot recognize what type of IP telephone terminal the other caller is using or cannot recognize what functions are available on the other IP telephone terminal. Hence, even when the other caller is using an IP telephone terminal equipped with various functions, such as a print function and an optical character recognition (OCR) function, the caller cannot sufficiently take advantage of these functions. In other words, the resources of the IP telephone system are not effectively utilized and, therefore, are wasted.
Japanese patent application publication No. 2005-192086 describes a convenient communication system in which a communication apparatus can execute a function not supported by the communication apparatus itself but possessed by another device. However, there is no description of a structure that can resolve the above problem, that is, how to recognize the type of the other device and the functions possessed thereby.
The description of Japanese patent application publication No. 2005-080025 asserts that a transmitting device transmitting images and a receiving device receiving the images can identify which communication method is supported by both parties using Session Description Protocol (SDP) media stream descriptions expanded by a Session Initiation Protocol (SIP) message, but this technology does not sufficiently resolve the problem described above.
Skype, which offers a free IP telephone application and free calls, has enjoyed much popularity. One factor enabling Skype to offer free calls may be its use of peer-to-peer communications, which eliminates the need for a server. However, one problem with IP telephone systems such as Skype that do not employ a server is that the system cannot recognize that a call is coming from a telephone terminal when a user is making an IP telephone call from a telephone terminal connected to a network terminal, such as a PC.
The technology disclosed in Japanese patent application publication No. 2005-192086 may be incorporated in an IP telephone system such as Skype by introducing a server into the system in order to register information on external terminals. The server could be referenced to recognize when a call is coming from an external terminal. However, introducing a server would make the system more complex and expensive, which would have a great impact on a system such as Skype that charges little or no usage fees.